1. Field of the Invention
The present invention relates to vehicles equipped with transmissions that enable their drive wheels to be separately powered to steer the vehicle and more particularly to small vehicles such as lawn and garden tractors equipped with such transmissions.
2. Description of the Related Art
It is known to provide small vehicles such as lawn mowing vehicles with hydrostatic motors for each drive wheel so that they can be powered individually. This permits the drive wheels to be powered forwardly and rearwardly in unison as well as at different speeds. Accordingly, the vehicle can be driven forwardly, rearwardly, steered by the drive wheels and turned about a vertical axis between the wheels. Vehicles equipped with such drive arrangements are sometimes referred to as having zero-turn or spin-turn capability.
Conventionally, the drive wheels have been controlled through separate hand levers. The hand levers serve to control both forward and reverse movement of each wheel as well as its speed. As the control lever is moved further forwardly or rearwardly of a neutral position, the speed increases. When one control lever is moved further from the neutral position than is the other lever, the vehicle turns since the speed of that wheel is increased relative to the other wheel. These types of hand controls require lengthy experience for an operator to become proficient in coordinating the forward speed and turning of the vehicle.
It is also known to provide large vehicles with transmissions that propel two drive wheels and individually steer each of them. These drive and steer type transmissions have taken the form of dual differential gear sets as well as planetary gear sets. They have been utilized primarily on tracked vehicles such as rice combines, tanks and skid-steer loaders. Recently, similar transmissions have become available in smaller configurations that provide for the wheel driving and steering functions to be controlled through separate input control devices. These devices permit forward, neutral and reverse propelling control for the two wheels with overriding control of each propelled wheel through a steering portion. With the advent of these transmissions, it would be desirable to adapt smaller vehicles such as lawn and garden tractors to utilize them. Further, it would be desirable to utilize forward, reverse and turn controls with which most individuals expected to use such vehicles would be familiar. Towards these ends, it would be desirable to utilize a conventional steering wheel with such transmissions as well as foot controls typically used with these vehicles. This would be particularly desirable since vehicles such as lawn and garden tractors are typically used infrequently, so that the operators would not be expected to develop the skills necessary for operating twin hand control levers. Therefore, it would be desirable to outfit a lawn and garden tractor with a steering wheel and foot controls for use with drive and steer type transmissions.
Such applications would provide a lawn and garden tractor with zero or drive and steer capability that would be more maneuverable around obstacles and in tight spaces since it could turn about an axis through its mowing unit or through itself. Further, productivity could be improved since the deck could be maneuvered to cut exactly where desired, thereby minimizing the movement of the deck over areas already cut. Additionally, it would be more comfortable and efficient for a new user to operate since they would most likely be familiar with the conventional steering wheels and foot controls used in lawn and garden tractors as well as automobiles.
Towards these ends, there is provided a vehicle such as a lawn and garden tractor which is adapted to utilize conventional steering and propel controls with a drive and steer type transmission. The transmission permits the vehicle to be driven and steered through its rear drive wheels, thereby permitting it to turn about one wheel and/or about an axis between its wheels. Front castered wheels enable the vehicle to be easily steered by the drive wheels.
A conventional type steering wheel is provided with a mechanical linkage extending between it and the transmission. Conventional type foot control pedals are also provided to propel or power the vehicle in a forward or rearward direction and within a range of speeds.
With conventional type steering and propel controls adapted to be utilized with the drive and steer type transmission, operation of spin-turn vehicles is made simple and more efficient as well as reducing the time required to learn to operate and maneuver the vehicle.